Memory cells have different read speeds. Some memory cells are “regular” or have an average read speed. Some memory cells are faster than an average memory cell or have a read speed value lower than an average read speed value. A fast (faster) memory cell is commonly called a strong memory cell. In contrast, some memory cells are slower than the average memory cell or have a read speed value higher than the average read speed value. In other words, slow memory cells have a larger read timing. A slow (slower) memory cell is commonly called a weak memory cell. Generally, a strong memory cell sinks and/or sources a higher current, while a weak memory cell sinks and/or sources a lower current. As a result, the read speed of a memory cell can be identified by the current sunk and/or sourced by the memory cell.
Tracking circuits have tracking cells that are used to generate tracking or reference signals based on which signals for reading memory cells are generated. Similar to a memory cell, a tracking cell has a different read speed identified by the current sunk and/or sourced by the tracking cell. In some approaches, tracking cells in a tracking circuit are designed to sink currents and generate tracking timings to cover timings for the weak memory cells. In many situations, using the average current value of the tracking cells may not cover the larger timing of the weak memory cells.
Like reference symbols in the various drawings indicate like elements.